First generation outdoor marine cloud brightening trial increases aerosol concentration at cloud base height
Open accessAbstract
Regional scale marine cloud brightening (MCB) has been proposed as a novel climate intervention to reduce the impact of global warming and associated marine heatwaves on the Great Barrier Reef. The concept relies on artificially generated sea spray aerosols (SSA) at the ocean surface and their transport in sufficient quantities to low-level maritime clouds. A portion of the SSA that reaches cloud height can act as additional cloud condensation nuclei and modify cloud microphysical properties, potentially reducing the amount of solar radiation reaching the sea surface. Although modelling data supports the MCB concept, field experiments demonstrating the dispersion of artificially produced SSA to clouds have not been previously reported. Here, we show that within a field of low-level trade wind cumulus-type clouds, an aerosol plume generated at the sea surface on board a research vessel was rapidly advected to cloud base height. Aircraft measurements conducted during two different sampling strategies, detected the aerosol plume from the vessel’s sea water atomisation system just below cloud bases at 700–900 m altitudes. For an estimated surface level aerosol production rate of 4 × 10 14 s−1, aerosol concentrations at cloud base were detected with peak number concentrations of up to ∼1 × 10 3 cm−3. Although such production rates of aerosol particles are orders of magnitude less than what is envisioned for any practical implementation of MCB, our results indicate that cloud perturbation experiments should now be possible using surface-produced SSA.
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The GBR experiments were conducted under a research permit from the Great Barrier Reef Marine Park Authority and involved explicit recognition of Indigenous peoples, including the Bindal and Mandubarra, for access to traditional sea country.
“the GBR experiments were conducted under a research permit from the Great Barrier Reef Marine Park Authority and involved explicit recognition of Indigenous peoples, including the Bindal and Mandubarra, for access to traditional sea country (Hernandez-Jaramillo et al., 2025)”
From Past Field Experiments of Solar Radiation Modification: A Review of the Scientific and Technical Aspects for Governance (2026) · cites this paper as Hernandez-Jaramillo et al., 2025
The primary focus of the Great Barrier Reef MCB trials was not climate intervention but mitigating coral bleaching by evaluating whether the MCB technique could locally enhance cloud reflectivity and reduce solar irradiance over the coral reef.
“The primary focus of these experiments was not climate intervention but mitigating coral bleaching by evaluating whether the MCB technique could locally enhance cloud reflectivity and reduce solar irradiance over the coral reef (Hernandez-Jaramillo et al., 2024, 2025).”
From Past Field Experiments of Solar Radiation Modification: A Review of the Scientific and Technical Aspects for Governance (2026) · cites this paper as Hernandez-Jaramillo et al., 2025
The first-generation GBR outdoor trial (2022) demonstrated that artificially generated sea spray aerosols from a ship-based effervescent nozzle system (ARIEL) could reach cloud base heights of 700-900 m, with peak aerosol concentrations of around 1×10^5/cm^3 detected by aircraft.
“The first-generation outdoor trial (2022) demonstrated that artificially generated sea spray aerosols (SSA) from a ship-based effervescent nozzle system (ARIEL) could reach cloud base heights of 700-900 m, with peak aerosol concentrations of around 1 × 10 5 /cm 3 detected by aircraft (Hernandez-Jaramillo et al., 2025).”
From Past Field Experiments of Solar Radiation Modification: A Review of the Scientific and Technical Aspects for Governance (2026) · cites this paper as Hernandez-Jaramillo et al., 2025
The Reef Restoration and Adaptation Program is supported by a public-private partnership, and the research was disclosed in peer-reviewed literature, ensuring scientific and public transparency.
“Additionally, the Reef Restoration and Adaptation Program is supported by a public-private partnership, and the research was disclosed in peer-reviewed literature, ensuring scientific and public transparency (Hernandez-Jaramillo et al., 2025)”
From Past Field Experiments of Solar Radiation Modification: A Review of the Scientific and Technical Aspects for Governance (2026) · cites this paper as Hernandez-Jaramillo et al., 2025
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References 40 · Cited by 8
- Authors
- Hernandez-Jaramillo, D. C., Harrison, L., Gunner, G., McGrath, A., Junkermann, W., Lieff, W., Hacker, J., Rosenfeld, D., Kelaher, B., & Harrison, D. P.
- Affiliations
- Southern Cross University (AU)
- The University of Sydney (AU)
- Flinders University (AU)
- Hebrew University of Jerusalem (IL)
- ORCID
- Venue
- Environmental Research Letters
- Publisher
- IOP Publishing
- Published
- 2025-04-29
- Volume
- 20
- Issue
- 5
- Pages
- 054065
- ISSN
- 1748-9326 (ISSN-L)
- OpenAlex
- W4409451747
- Cited by
- 8
- References
- 40
- Citations by year
- 2026: 5 · 2025: 3
- FWCI
- 3.30
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Environmental Research Letters (publishedVersion, cc-by)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Funders
- Great Barrier Reef Foundation
- Australian Government
- Reef Trust
- Topics
- Physical Sciences › Environmental Science › Global and Planetary Change › Atmospheric aerosols and clouds
- Physical Sciences › Environmental Science › Global and Planetary Change › Climate Change and Geoengineering
- Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Atmospheric chemistry and aerosols
- Keywords
- marine cloud brightening, sea spray aerosol, cloud condensation nuclei, trade wind cumulus clouds, climate intervention, Great Barrier Reef, marine heatwaves, airborne measurements
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